revised note on exclusions

Author: howcom

css3-gcpm/Overview.src.html

@@ -3090,7 +3090,8 @@ <h3>Exclusions based on rendered content</h3>
 </div>
 
 <p class=issue>Define behavior if both 'exclude-level' and 'background-exclude-level' is set.
-<p class=issue>Some kind of spacing behavior must be defined. Define behavior if both 'exclude-level' and 'bakcground-exclude-level' is set.
+
+<p class=issue>Some kind of spacing behavior must be defined. Define behavior if both 'exclude-level' and 'background-exclude-level' is set; 'exclude-margin' may be an option.
 
 <h3>Exclusions based on shapes</h3>